Method of utilizing a relay node in wireless communication system

ABSTRACT

The present invention relates to a wireless communication system and a user equipment (UE) providing wireless communication services, and more particularly, a method of preventing transmission error of data while maintaining its security and a method of controlling an access of a Relay Node (RN) to a Donor eNB (DeNB) and an access of the UE to the RN during a process of transmitting and receiving user data when the RN as a radio network node is connected to the DeNB in an Evolved Universal Mobile Telecommunications System (E-UMTS), a Long Term Evolution (LTE) system, and a LTE-Advanced (LTE-A) system that have evolved from a Universal Mobile Telecommunications System (UMTS).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/256,919, filed on Sep. 15, 2011, now U.S. Pat. No. 9,654,256, whichis the National Stage filing under 35 U.S.C. 371 of InternationalApplication No. PCT/KR2010/002503, filed on Apr. 21, 2010, which claimsthe benefit of U.S. Provisional Application Nos. 61/171,440, filed onApr. 21, 2009, 61/173,181, filed on Apr. 27, 2009, and 61/173,962, filedon Apr. 29, 2009, the contents of which are all incorporated byreference herein in their entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication system and auser equipment (UE) providing wireless communication services, and moreparticularly, a method of preventing transmission error of data whilemaintaining its security and a method of controlling an access of aRelay Node (RN) to a Donor eNB (DeNB) and an access of the UE to the RNduring a process of transmitting and receiving user data when the RN asa radio network node is connected to the DeNB in an Evolved UniversalMobile Telecommunications System (E-UMTS), a Long Term Evolution (LTE)system, and a LTE-Advanced (LTE-A) system that have evolved from aUniversal Mobile Telecommunications System (UMTS).

BACKGROUND ART

First, the LTE system is a mobile communication system that has evolvedfrom a UMTS system, and the standard has been established by 3rdGeneration Partnership Project (3GPP), which is an internationalstandardization organization.

FIG. 1 is a view illustrating the network architecture of an LTE system,which is a mobile communication system to which the related art and thepresent invention are applied.

As illustrated in FIG. 1, the LTE system architecture can be roughlyclassified into an Evolved UMTS Terrestrial Radio Access Network(E-UTRAN) and an Evolved Packet Core (EPC). The E-UTRAN may include auser equipment (UE) and an Evolved NodeB (eNB, base station), whereinthe connection between UE-eNB is called a Uu interface, and theconnection between eNB-eNB is called an X2 interface. The EPC mayinclude a Mobility Management Entity (MME) performing a control-planefunction and a Serving Gateway (S-GW) performing a user-plane function,wherein the connection between eNB-MME is called an S1-MME interface,and the connection between eNB-S-GW is called an S1-U interface, andboth connections may be commonly called an S1 interface.

A radio interface protocol is defined in the Uu interface which is aradio section, wherein the radio interface protocol is horizontallycomprised of a physical layer, a data link layer, a network layer, andvertically classified into a user plane (U-plane) for user datatransmission and a control plane (C-plane) for signaling transfer. Sucha radio interface protocol can be typically classified into L1 (firstlayer) including a PHY layer which is a physical layer, L2 (secondlayer) including MAC/RLC/PDCP layers, and L3 (third layer) including aRRC layer as illustrated in FIGS. 2 and 3. Those layers exist as a pairin the UE and E-UTRAN, thereby performing data transmission of the Uuinterface.

FIGS. 2 and 3 are exemplary views illustrating the control plane anduser plane architecture of a radio interface protocol between UE andE-UTRAN in an LTE system, which is a mobile communication system towhich the related art and the present invention are applied.

The physical layer (PHY) which is a first layer provides informationtransfer services to the upper layers using a physical channel. The PHYlayer is connected to the upper Medium Access Control (MAC) layerthrough a transport channel, and data between the MAC layer and the PHYlayer is transferred through the transport channel. At this time, thetransport channel is roughly divided into a dedicated transport channeland a common transport channel based on whether or not the channel isshared. Furthermore, data is transferred between different PHY layers,i.e., between PHY layers at the transmitter and receiver sides.

Various layers exist in the second layer. First, the Medium AccessControl (MAC) layer serves to map various logical channels to varioustransport channels, and also performs a logical channel multiplexing formapping several logical channels to one transport channel. The MAC layeris connected to an upper Radio Link Control (RLC) layer through alogical channel, and the logical channel is roughly divided into acontrol channel for transmitting control plane information and a trafficchannel for transmitting user plane information according to the type ofinformation to be transmitted.

The Radio Link Control (RLC) layer of the second layer managessegmentation and concatenation of data received from an upper layer toappropriately adjust a data size such that a lower layer can send datato a radio section. Also, the RLC layer provides three operation modessuch as a transparent mode (TM), an un-acknowledged mode (UM) and anacknowledged mode (AM) so as to guarantee various quality of services(QoS) required by each radio bearer (RB). In particular, AM RLC performsa re-transmission function through an automatic repeat and request (ARQ)function for reliable data transmission.

A Packet Data Convergence Protocol (PDCP) layer of the second layerperforms a header compression function for reducing the size of an IPpacket header which is relatively large in size and contains unnecessarycontrol information to efficiently transmit IP packets, such as IPv4 orIPv6, over a radio section with a relatively small bandwidth. Due tothis, information only required from the header portion of data istransmitted, thereby serving to increase the transmission efficiency ofthe radio section. In addition, in the LTE system, the PDCP layerperforms a security function, which includes ciphering for preventingthe third person's data wiretapping and integrity protection forpreventing the third person's data manipulation.

A radio resource control (RRC) layer located at the uppermost portion ofthe third layer is only defined in the control plane. The RRC layerperforms a role of controlling logical channels, transport channels andphysical channels in relation to configuration, re-configuration, andrelease of Radio Bearers (RBs). Here, the RB denotes a logical pathprovided by the first and the second layers for transferring databetween the UE and the UTRAN. In general, the establishment of the RBrefers to a process of stipulating the characteristics of protocollayers and channels required for providing a specific service, andsetting each of the detailed parameter and operation method thereof. TheRB is divided into a signaling RB (SRB) and a data RB (DRB), wherein theSRB is used as a path for transmitting RRC messages in the C-plane whilethe DRB is used as a path for transmitting user data in the U-plane.

In general, when there is data to be transmitted to the UE, the basestation transmits the data to the UE, and then waits receiptnotification from the UE. If it is notified that the UE has successfullyreceived data, then the base station deletes the data from its ownbuffer. However, if it is notified that the UE has not successfullyreceived data, then the base station retransmits the data.

However, it is difficult to make a direct data transmission andreception between the base station and the UE due to the introduction ofa relay node (RN). In other words, even if the base station hassuccessfully transferred the data to the relay node, the base station isunable to know whether or not the data has been successfully transferredfrom the relay node to the UE. Similarly, from a standpoint of the UE,even if the UE has successfully transferred the data to the relay node,the UE is unable to know whether or not the data block has successfullytransferred from the relay node to the base station.

Typically, each UE has a possibility of continuously moving its locationover a mobile communication system. For example, if data blocks 1, 2,and 3 have been successfully transferred from the base station to therelay node, then the base station can delete the data blocks 1, 2, and 3from its own buffer. Then, the relay node will start to transmit thedata blocks 1, 2, and 3 to the UE. In this situation, it may happen thatthe UE moves to a new area while the relay node transmits the data blockto the UE. In case where the UE is out of the connected relay node,there may be a problem of occurring a data block that cannot besuccessfully transferred to the UE among the data blocks received fromthe base station to the relay node.

Furthermore, every base station (eNB) does not support RN. For example,Rel-8 eNB does not support RN. In this case, the RN should not attemptan access to a Donor eNB (DeNB). If the RN is accessed to an eNB thatdoes not support RN, data generated by the RN itself may be processed tobe transferred by the eNB but data generated by the UE that has beenaccessed to the RN cannot be processed by the eNB. In this case, the UEthat has been accessed to the RN merely consumes the radio resources andbattery, but is unable to receive any services.

In addition, if an additional access of the UE to the RN occurs when anamount of radio resources allocated to the RN is limited over an Uninterface, then a radio al-location amount to the LIE is limited,thereby causing a problem that the UE cannot properly receive servicesor another UE cannot properly receive services if the priority of the UEis higher. As a result, the RN cannot allow an access from the UEs withno particular plan in view, thereby requiring a suitable control methodfor managing this.

DISCLOSURE OF INVENTION Solution to Problem

Accordingly, an object of the present invention is to provide a methodof effectively transmitting or receiving data blocks between RN and UEin an LTE-A system and an effective access control method thereof.

In order to solve the foregoing problem, the present invention proposesa method of reporting a status report in a wireless communicationsystem, the method comprising: receiving, by a first protocol entity,data from a second protocol entity; transmitting, by the first protocolentity, the received data to a third protocol entity; receiving a statusreport from the third protocol entity, wherein at least one statusreport indicate any unsuccessfully received data by the third protocolentity; and transmitting the status report to the second protocolentity.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

In the drawings:

FIG. 1 is a view illustrating the network architecture of an LTE system,which is a mobile communication system to which the related art and thepresent invention are applied;

FIG. 2 is an exemplary view illustrating the control plane architectureof a radio interface protocol between UE and E-UTRAN in an LTE system,which is a mobile communication system to which the related art and thepresent invention are applied;

FIG. 3 is an exemplary view illustrating the user plane architecture ofa radio interface protocol between UE and E-UTRAN in an LTE system,which is a mobile communication system to which the related art and thepresent invention are applied;

FIG. 4 is an exemplary view illustrating the bearer service structure ofan LTE system;

FIG. 5 is an exemplary view illustrating a relay node (RN) in an LTE-Asystem to which the present invention is applied;

FIG. 6 is an exemplary view illustrating a method of receiving data in adownward direction;

FIG. 7 is an exemplary view illustrating an overall protocolarchitecture including a UE accessed to the RN;

FIG. 8 is an exemplary view illustrating the architecture of a PDCPentity;

FIG. 9 is an exemplary view illustrating the architecture of PDCP STATUSPDU;

FIG. 10 is an exemplary view illustrating the operation of transmittingor receiving data while preventing transmission error of data at thetime of using the RN according to the present invention;

FIG. 11 is an exemplary view illustrating the operation of transmittingor receiving data while maintaining the security according to thepresent invention:

FIG. 12 is an exemplary view illustrating the operation of controllingan access of RN to DeNB and an access of UE to RN according to thepresent invention; and

FIG. 13 is another exemplary view illustrating the operation ofcontrolling an access of RN to DeNB and an access of UE to RN accordingto the present invention.

MODE FOR THE INVENTION

One aspect of this disclosure relates to the recognition by the presentinventors about the problems of the related art as described above, andfurther explained hereafter. Based upon this recognition, the featuresof this disclosure have been developed.

Although this disclosure is shown to be implemented in a mobilecommunication system, such as a UMTS developed under 3GPPspecifications, this disclosure may also be applied to othercommunication systems operating in conformity with different standardsand specifications.

The present invention may be applied to a 3GPP communication technology,particularly to a Universal Mobile Telecommunications System (UMTS),system, and a communication device and method thereof. However, thepresent invention is not limited to this, but may be applied to everywire/wireless communication to which technical spirit of the presentinvention can be applied.

Hereinafter, the construction and operation of preferred embodimentsaccording to the present invention will be described with reference tothe accompanying drawings.

First, a bearer service architecture of the LTE system will bedescribed. FIG. 4 is an exemplary view illustrating a bearer servicearchitecture of the LTE system. Typically, Radio Bearer is a bearerprovided in a Uu interface to support the user's service. In 3GPP, eachbearer is defined for each interface as illustrated therein to guaranteeindependence between those interfaces. Specifically, bearers provided byLTE system are commonly called an Evolved Packet System (EPS) bearer,which can be divided into Radio Bearer, S1 Bearer, and the like, foreach interface as illustrated in FIG. 4.

In FIG. 4, Packet Gateway (P-GW) is a network node for connectingbetween the LTE network and another network, and EPS Bearer provided bythe LTE system is defined between LIE and P-GW. The EPS Bearer issubdivided between individual nodes of the LTE system, and defined asRadio Bearer between UE-eNB, S1 Bearer between eNB-S-GW, and S5/S8Bearer between S-GW and P-GW. Each bearer is defined through quality ofservice (QoS), and the QoS may include data rate, error rate, delay, andthe like. Accordingly. QoS that should be totally provided by an LTEsystem is defined as a EPS bearer, and then each QoS is determined foreach interface, and the bearer is set for each interface according tothe QoS that should be provided by itself. Since the bearer of eachinterface is provided by dividing a total EPS bearer into sections, theEPS bearer and other bearers, such as Radio Bearer, S1 Bearer, and thelike are all one-to-one relationships.

Hereinafter, a Long-Term Evolution Advanced (LTE-A) system will bedescribed. The LTE-A system is a system that has been developed from anLTE system to meet IMT-Advanced conditions, which are the fourthgeneration mobile communication conditions recommended by theInternational Telecommunication Union-Radiocommunication Sector (ITU-R).At present, the LTE-A system standard is actively under development by3GPP that has developed the LTE system standard. Representativetechnologies newly added in the LTE-A system mi carrier aggregationtechnology for extending a used bandwidth to be flexibly used, and relaytechnology for increasing coverage, supporting group mobility, andallowing network arrangement.

Here, relay is a technology for relaying data between a user equipment(EU) and an Evolved Node B (eNB, base station). Since communication isnot smoothly implemented in case where a distance between UE and eNB isfar in the LTE system, it is introduced in an LTE-A system as a methodof making up for the problem. A new network node, which is referred toas Relay Node (RN), is introduced between UE and eNB to perform such arelay operation, wherein the eNB for managing RN is called Donor eNB(DeNB). In addition, an interface between RN-DeNB that has been newlyadded due to RN is defined as an Un interface, thereby beingdifferentiated from a Un interface that is an interface between UE and anetwork node. FIG. 5 illustrates such a concept of Relay Node and an Uninterface.

Here, the RN serves to manage UE in behalf of the DeNB. In other words,from a standpoint of the UE, the RN is shown as DeNB, and therefore,MAC/RLC/PDCP/RRC, which is an Uu interface protocol that has been usedin a conventional LTE system, are used as they are in a Uu interfacebetween UE-RN.

From a standpoint of the DeNB, the RN may be shown as UE or shown alsoas eNB according to circumstances. In other words, when the RN is firstaccessed to the DeNB, it is accessed through random access like UEbecause the existence of the RN is unknown to the DeNB, but operatedlike eNB managing UE connected to itself after the RN is once accessedto the DeNB. Accordingly, along with the Uu interface protocol, thefunctions of the Un interface protocol should be also defined as in theform to which a network protocol function is also added. For the Uninterface protocol, discussions as to which functions should be added orchanged to each protocol layer on the basis of Uu protocols such asMAC/RLC/PDCP/RRC are still in progress in 3GPP.

Next, there will be described a method in which the UE receives data ina downward direction in an LTE system. FIG. 6 is an exemplary viewillustrating a method of receiving data in a downward direction.

As illustrated in FIG. 6, a physical channel in a downward direction canbe roughly divided into two types, such as a Physical Downlink ControlChannel (PDCCH) and a Physical Downlink Shared Channel (PDSCH). Here,control information, which is not directly related to the transmissionof user data but required for operating a physical channel, istransmitted over the PDCCH. To explain most briefly, the PDCCH can bealso used to control other physical channels. In particular, the PDCCHis used to transmit information that is required to receive the PDSCH.Information as to at a specific timing, data to be transferred using aspecific frequency bandwidth, for a certain UE, a certain size of datato be transferred, and the like will be transmitted over the PDCCH.Accordingly, each UE receives the PDCCH at a specific Time TransmissionInterval (TTI), checks whether or not data that should be received byitself is transmitted, and additionally receives the PDSCH usinginformation such as the frequency indicated by the PDCCH, and the likeif notified that data that should be received by itself is transmitted.Information as to data of the PDSCH to be transmitted to a certain UE(s)(a single or a plurality of UEs), how to receive and decode PDSCH databy the UEs, and the like can be included in a Physical Downlink ControlChannel (PDCCH) to be transmitted.

For example, in a specific subframe, it is assumed that radio resourceinformation (for example, frequency position) called “A” and transporttype information (for example, transport block size, modulation andcoding information, etc.) called “B” are CRC-masked to an Radio NetworkTemporary Identity RNTI (RNT) called “C”, and transmitted via the PDCCH.One or two or more UEs located in the relevant cell monitor the PDCCHusing their RNTI information, and on the above assumption, when the UEhaving the RNTI called “C” decodes the PDCCH, a CRC error does notoccur. Thus, the UE decodes the PDSCH to receive data by using thetransport type information called “B” and the radio resource informationcalled “A”. On the contrary, on the above assumption, if the UE does nothave the RNTI called “C” when the PDCCH is decoded, a CRC error occurs.Thus, the UE does not receive the PDSCH.

In the above procedure, the Radio Network Temporary Identifier (RNTI) istransmitted to inform to which UEs radio resources have been allocated.The RNTI includes a dedicated RNTI and a common RNTI. The dedicated RNTIis allocated to a single UE and used to transmit or receive datacorresponding to the UE. The dedicated RNTI is allocated only to the UEwhose information has been registered in the base station. On thecontrary, the common RNTI is used when UEs, which have not beenallocated the dedicated RNTI because their information was notregistered to the base station, transmit or receive data to or from thebase station, or the common RNTI is used to transmit informationcommonly applied for a plurality of UEs.

Hereinafter, a RRC_IDLE state of the UE will be described in detail. TheUE in the RRC_IDLE state should always select the cell having a suitablequality to be prepared to receive services through this cell. Forexample, the UE that has just powered on should select the cell having asuitable quality to be registered in a network. If the UE that has beenin a RRC_CONNECTED state enters into RRC_IDLE, then the UE should selecta cell to stay in RRC_IDLE. As described above, a process in which theUE selects the cell satisfying certain conditions to stay in a servicewaiting state such as the RRC-IDLE state is called cell selection.

Hereinafter, a method of selecting a cell by the UE will be described.When power is initially turned on, the UE searches available PLMNs andthen selects a suitable PLMN capable of receiving services.Subsequently, the UE selects a cell having signal qualities andcharacteristics capable of receiving a suitable service among the cellsprovided by the selected PLMN. Here, the cell selection process isroughly divided into two types. First, for an initial cell selectionprocess, the UE have no previous information about radio channels. Thus,the UE searches all radio channels to find a suitable cell. In eachchannel, the UE finds the strongest cell. Then, once the UE finds asuitable cell satisfying the cell selection criteria, the UE selects therelevant cell. Next, in a cell selection process using the storedinformation, a cell is selected by using information stored in the UEfor radio channels or using information broadcast from the cells duringthe process. Thus, a cell selection can be promptly performed comparedto an initial cell selection process. Once the UE finds a suitable cellsatisfying the cell selection criteria, the UE selects the relevantcell. If a suitable cell satisfying the cell selection criteria is notfound through this process, then the UE performs an initial cellselection process.

Hereinafter, a process of reselecting a cell will be described. After acertain cell is once selected through a cell selection process, a signalintensity or quality between the UE and the base station may vary due tomobility of the UE, change of radio environments, or the like. Thus, ifthe quality of the selected cell is deteriorated, then the UE can selectanother cell providing a better quality. In case of reselecting a cellin this manner, the cell providing a better signal quality than thecurrently selected cell is typically selected. This process is calledcell selection. The cell reselection process, from a viewpoint of thequality of a radio signal, has a basic purpose to typically select acell providing the best quality to the UE. In addition to the viewpointof the quality of a radio signal, a network can determine a priority foreach frequency to inform the priority to the UE. The UE that hasreceived such a priority preferentially considers this priority duringthe cell reselection process compared to the radio signal qualitycriteria.

FIG. 7 is an exemplary view illustrating an overall protocolarchitecture including a UE accessed to the RN. An IP packet generatedby the UE is passed through PDCP/RLC/MAC/PHY of the UE, and passedthrough PHY/MAC/RLC/PDCP at a side of the Uu interface of the RN, andtransferred to an upper stage of the RN. The RN additionally attachesGTP-u/UDP/IP to the IP packet received form the UE and transfers theattached IP packet to DeNB through PDCP/RLC/MAC/PHY at a side of the Uninterface. Here, IP/UDP additionally attached by the RN is used toproperly transfer the IP packet received by the DeNB from the UE toS-GW/P-GW corresponding to the UE. The GTP-u header is used todifferentiate IP packets that have been actually generated by the UE orthat should be transferred to the UE, within the packets using the sameIP/UDP.

Hereinafter, a RLC layer will be described in more detail. As previouslydescribed above, there exist three modes, TM, UM, and AM in the RLClayer. However, in case of TM, there is few functions that can beperformed in RLC, and therefore, only UM and AM will be describedherein.

UM RLC sends each PDU by attaching a PDU header including a sequencenumber (hereinafter, abbreviated as “SN”), thereby allowing the receiverside to know which PDU is lost during transmission. Owing to thisfunction, the UM RLC mainly takes charge of transmission ofbroadcast/multicast data or transmission of real-time packet data suchas voice of packet service domain (hereinafter, abbreviated as “PSdomain”) (for example, VoIP) and streaming in the user plane, or takescharge of transmission of a RRC message requiring no acknowledgementamong the RRC messages transmitted to a specific UE or specific UE groupwithin a cell in the control plane.

Similarly to the UM RLC, AM RLC configures PDU by attaching a PDU headerincluding SN at the time of configuring the PDU. Yet, the AM RLC differsfrom the UM RLC in that a receiver side makes acknowledgement to PDUtransmitted by a transmitter side. The reason why the receiver sidemakes acknowledgement in the AM RLC is because the transmitter sidemakes a request for retransmission of PDU failing to be received by thereceiver side itself, and this retransmission function is the mostoutstanding feature of the AM RLC. So, the object of the AM RLC is toguarantee error-free data transmission through retransmission. Owing tothis object, the AM RLC mainly takes charge of transmission ofnon-real-time packet data such as TCP/IP of PS domain in the user planeor performs transmission of a RRC message necessarily requiringacknowledgment among the RRC messages transmitted to a specific UEwithin a cell in the control plane.

In view of the aspect of directionality, UM RLC is used foruni-directional communications, whereas AM RLC is used forbi-directional communications due to feedback from a receiver side.Also, there exists a difference in the structural aspect. One RLC entityincludes a transmission or reception structure in the UM RLC, whereasboth transmitter and a receiver sides exist within one RLC entity in theAM RLC.

The complexity of the AM RLC is due to the retransmission function. Forre-transmission management, the AM RLC has a retransmission buffer inaddition to a transmission/reception buffer, and performs variousfunctions, such as using of a transmitting/receiving window for flowcontrol, polling in which a transmitter side requests status informationto a receiver side of a peer RLC entity, a status report in which areceiver side reports its own buffer status to a transmitter side of thepeer RLC entity, a status PDU configuration for carrying statusinformation, and the like. In addition, various protocol parameters,status variables and timers are required in the AM RLC to support thesefunctions. The PDU used to control data transmission in the AM RLC suchas status report, status PDU, or the like is called control PDU and thePDU used to transfer user data is called data PDU.

If there exists data unable to be received properly, the AM RLC at areceiver side informs the fact to the AM RLC at a transmitter side torequest retransmission. This is call status report, and transmittedusing STATUS PDU which is one of control PDUs. According to the statusreport received from the receiver side, the transmitter side retransmitsdata blocks, reported that have been not been properly received by thereceiver side.

Hereinafter, a PDCP entity will be described in detail. The PDCP entityis upwardly connected to a RRC layer or user application, and downwardlyconnected to a RLC layer, and the detailed architecture thereof is asfollows. FIG. 8 is an exemplary view illustrating the architecture of aPDCP entity. The blocks illustrated in FIG. 8 are functional blocks, andmay differ from actual implementation.

One PDCP entity may include a transmitter side and a receiver side asillustrated in FIG. 8. The transmitter side on the left performs a roleof configuring SDU received from the upper layer or control informationgenerated by the PDCP entity itself as PDU to transmit to a receiverside of the peer PDCP entity, and the receiver side on the rightperforms a role of extracting PDCP SDU or control information from thePDCP PDU received from a transmitter side of the peer PDCP entity.

As described above, there are two kinds of PDUs, data PDU and controlPDU, which are generated by the transmitter side of the PDCP entity.First, PDCP Data PDU is a data block made in PDCP by processing SDUreceived from the upper layer, and PDCP Control PDU is a data blockgenerated by PDCP itself for the PDCP to transfer control information tothe peer entity.

The PDCP Data PDU is generated in RB of both the user plane and controlplane, and some of the PDCP functions are selectively applied accordingto the used plane. In other words, a header compression function isapplied only to U-plane data, and an integrity protection functionwithin the security function is applied only to C-plane data. Thesecurity function may also include a ciphering function for maintainingthe security of data in addition to the integrity protection functionthereof, and the ciphering function is applied to both U-plane andC-plane data.

The PDCP Control PDU is generated only in U-plane RB, and may includeroughly two types, such as a PDCP status report for informing atransmitter side of the situation of a PDCP reception buffer, and aheader compression (HC) feedback packet for informing a headercompressor of the situation of a header decompressor.

The PDCP status report is transmitted from a receiver-side PDCP to atransmitter-side PDCP. Through this, the receiver-side PDCP informs thetransmitter-side PDCP which PDCP SDU is received or not received,thereby allowing the received PDCP SDU not to be retransmitted orallowing the unreceived PDCP SDU to be retransmitted. Such a PDCP statusreport is transmitted in the form of PDCP STATUS PDU, and thearchitecture thereof is illustrated in FIG. 9.

The definition of each field or element illustrated in FIG. 9 is asfollows.

-   -   D/C (Data/Control): 1 bit        -   Informs whether relevant PDU is data PDU or control PDU.    -   PDU Type: 3 bits        -   Informs a kind of the control PDU.        -   “000” is PDCP Status Report. “001” is Header Compression            Feedback information, and remaining values are reserved.    -   FMS (First Missing SN): 12 bits        -   SN of the PDCP SDU that cannot be received first at a            receiver side.    -   Bitmap: variable length        -   Denotes reception failure if the relevant bit position of            the bitmap field is “0”, and reception success if the            relevant bit position of the bitmap field is “1”.

The PDCP status report as described above is currently used at the timeof performing handover in an LTE system. First, the transmitter-sidePDCP stores PDCP SDUs transferred from the upper layer in a transmissionbuffer even after their transmission for re-transmission that may belater required. Then, when handover occurs, the transmitter-side PDCPreceives information on PDCP SDU that has been received by areceiver-side PDCP as well as PDCP SDU that has not been received by thereceiver-side PDCP through a PDCP status report, and retransmits PDCPSDU that has not received by the receiver-side PDCP after the handover.Particularly, in a side of the network, eNB is changed from the sourceto the target if handover occurs, thereby changing the PDCP entity, andthus re-transmission using such a status report is necessarily required.

As previously described above, according to the present invention, it isproposed a method of effectively transmitting or receiving data blocksbetween RN and EU in an LTE-A system.

For this purpose, according to the present invention, DeNB has aplurality of protocol layers, and each of the protocol layers isconnected to a protocol layer of another node, respectively. Then, eachprotocol layer transmits and/or receives reception status reports toand/or from a protocol layer of the node connected with itself. In otherwords, the transmitter side of each protocol layer deletes data blocksinformed that has been successfully received by the receiver side, basedon a reception status report received from the receiver side.Accordingly, data blocks informed that has not been successfullyreceived by the receiver side is retransmitted. Furthermore, if thereexists any data block that has not been successfully received, thereceiver side of each protocol layer informs the fact to the transmitterside using a reception status report. In the above process, the protocollayer is a DPCP/RLC/RRC layer, and the node is DeNB/RN/UE.

According to another embodiment of the present invention, it is proposedthat a plurality of protocol layers are provided between RN and DeNB,and one of those protocol layers is used to transfer information betweenUE and RN.

In other words, RN and DeNB are provided with two or more protocollayers, and at least one protocol layer of them takes charge oftransmission and reception of data blocks, and the remaining protocollayers are used to transmit or receive information of a certain protocollayer between UE and RN.

FIG. 10 is an exemplary view illustrating the operation of transmittingor receiving data while preventing transmission error of data at thetime of using the RN according to the present invention.

As illustrated in FIG. 10, RLC 1 takes charge of transmission andreception of data between RN and DeNB. Here, the RLC 1 is considered asa conventional AM RLC. Thus, the RLC 1 performs a role of transferringdata transferred from the DeNB to the RN and data transferred from theRN to the DeNB without error or loss. RLC 3 takes charge of transmissionand reception of data between the RN and UE. Here, the RLC 3 is alsoconsidered as a conventional AM RLC. As a result, the RLC 3 performs arole of transferring data transferred from the UE to the RN and datatransferred from the RN to the UE without error or loss.

As illustrated in FIG. 10. RLC 2 performs a role of transferringinformation of the RLC 3. Preferably, the RLC 2 transfers transmissionand reception confirmation information (RLC status report) which isexchanged in the RLC 3. For example, the RN transmits data transferredfrom the DeNB to a UE through the RLC 3. The UE receives data blocksfrom the RN through the RLC 3, and transfers transmission and receptionconfirmation information on this to the RN through the RLC 3. The RNtransfers the transmission and reception confirmation informationreceived from the UE through the RLC 3 to the DeNB by including thetransmission and reception confirmation information of the RLC 2.

For example, it is assumed that there are five data blocks to betransferred from the DeNB to the UE, having sequence numbers, such as 1,2, 3, 4, and 5. First, the DeNB data blocks 1/2/3/4/5 will betransmitted to the RN. For the data blocks 1/2/3/4/5 transferred fromthe DeNB, the RN transfers information as to data blocks which have beensuccessfully received and data blocks which have not been successfullyreceived. All of those operations are performed by RLC 1.

Here, however, the RN will transmit data blocks 1/2/3/4/5 received fromthe DeNB to the UE. For the data blocks 1/2/3/4/5 transferred from theRN, the UE will configure and transmit information as to data blockswhich have been received and data blocks which have not been received,to the DeNB using RLC 3.

If the UE informs the RN that data blocks 2/4 are not received using theRLC 3, then the RN will inform the DeNB that the UE has not receiveddata blocks 2/4 using transmission and reception confirmationinformation in RLC 2.

In brief, both RLC 2 and RLC 1 are set between relay and DeNB totransfer transmission and reception confirmation information. RLC 1transfers information as to data blocks that have successfully receivedor have not successfully received by the relay itself among data thathad been transmitted from DeNB to the DeNB, whereas RLC 2 transfersinformation as to data blocks that have successfully received or havenot successfully received by UE connected to the relay among data thathad been transmitted from DeNB to the RN. The operations described inthe above process will be also applicable to a PDCP layer. In otherwords, transmission and reception confirmation information between UEand RN may be transmitted through PDCP which has been set between RN andDeNB.

According to still another embodiment of the present invention, it isproposed that transmission and reception confirmation information sentfrom a relay to DeNB may include transmission and reception confirmationinformation transmitted from UE to the relay.

For example, if RLC 1 of DeNB transmits data blocks to RLC 1 of RN andthe RLC 3 of the RN transmits data blocks received from the RLC 1 to UE,then RLC 3 of the UE transmits transmission and reception confirmationinformation to the RLC 3 of the RN based on the data blocks that havebeen received from the RN. The RLC 1 of the RN configures transmissionand reception confirmation information based on the transmission andreception confirmation information that have been transferred from theRLC 3 of the UE to the RLC 3 of the RN, thereby transmitting to RLC 1 ofDeNB. In other words, in this case, the transmission and receptionconfirmation information transmitted from RLC 1 is not informationbetween DeNB and RN, but information between RN and UE. For example,even though RN has successfully received data blocks 1/2 form DeNB, theRN informs the DeNB that the data blocks 1/2 are not successfullyreceived if the data blocks are not properly transferred to UE.

In addition, according to the present invention, there is provided amethod of safely protecting data that is transmitted or received by UE.

FIG. 11 is an exemplary view illustrating the operation of transmittingor receiving data while maintaining the security at the time of using RNaccording to the present invention. The elements illustrated in FIG. 11are defined as follows. Ck: ciphering key, CK-UE-AS: ciphering key usedfor a specific UE in AS level, CK-UE-NAS: ciphering key used for aspecific UE in NAS level, CK-RNB-AS: ciphering key used for a specificRNB in AS level, Ik->Integrity Key, IK-UE-AS: Integrity key used for aspecific UE in AS level, IK-UE-NAS: Integrity key used for a specific UEin NAS level, IK-RNB-AS: Integrity key used for a specific RNB in ASlevel, In each case, the transmit ciphers/integrity-protects thetransmitted PDU with configured keys and the receiverde-ciphers/integrity-checks the received PDU with configured keys.

In other words, if data to be transferred to the UE is received fromMME/S-GW, then DeNB preferentially apply security to the data using anintegrity key (IK) value and a ciphering key (CK) value set to 1:1 withthe UE. Furthermore, the DeNB apply security to the data using IK and CKvalues set between a relay and DeNB.

In downlink direction: DeNB ciphers PDCP SDU (data block for a UE) usingthe key shared between UE and DNB. The result is PDCP PDU 1. Then, theDNB ciphers PDCP PDU 1 using the key shared between RN and DeNB. Theresult is PDCP PDU 2, and such PDCP PDU 2 (RLC SDU 1) is delivered tolower layer. When RN receives a RLC SDU 2 (PDCP PDU 3), the RN deciphersthe RLC SDU 2 using the key shared between RN and DeNB. The result isPDCP PDU 4, and then, the RN transmits PDCP PDU 4 toward a UE. When theUE receives a PDCP PDU 4, it deciphers this PDU using the key sharedbetween the UE and DeNB. Preferably, the same SN can be used for step 1and step 2.

In UL direction: when UE transmits a PDCP SDU 5, it ciphers this SDUusing the key shared between UE and DeNB. When RN receives PDCP PDU 5from UE, the RN ciphers this using the key shared between RN and DeNB.The result is PDCP PDU 6. When, the DeNB receives a PDCP PDU 6 from RN,it deciphers this using the key shared between the RN and DeNB. Theresult is PDCP PDU 7. The DeNB deciphers PDCP PDU 7 using the key sharedbetween the UE and DeNB. The result is PDCP SDU. Preferably, the same SNcan be used for step 1 and step 2.

In addition, according to the present invention, there is provided aneffective access control method in an LTE-A system. Thus, according tothe present invention, it is proposed that eNB transmits RN accesscontrol information (Relay Access information) to UEs. FIG. 12 is anexemplary view illustrating the operation of controlling an access of RNto DeNB and an access of UE to RN according to the present invention.The RN access control information may include information as to whetheror not RN can access the relevant cell or information as to whether ornot the relevant eNB and the relevant cell supports RN. The RN that hasreceived the RN access control information attempts to access the cellonly if the relevant RN access control information allows an access ofthe RN. Then, the RN that has received the RN access control informationdoes not attempt to access the cell if the relevant RN access controlinformation does not allow an access of the RN. Then, if the relevantcell does not transmit RN access control information, the RN entered ina certain cell considers that the relevant cell does not support, andthus the RN does not attempt an access to the relevant cell. During theprocess, if a cell to which the RN has entered does not support anaccess to the RN or doe not allow the access, the RN selects and entersinto another new cell. Attempting an access during the process means toperform a RRC Connection Establishment process. Additionally, during theprocess, the RN informs eNB or a core network that it is a RN.Preferably, the information may be included in the RRC ConnectionEstablishment process. Furthermore, during the process, the RNadditionally informs eNB or a core network that it is a fixed-type RN ormobile-type RN. If the RN is fixed, then the RN will not performhandover, and thus eNB may not perform measurement configuration to theRN, and also the RN will not send a measurement report to the eNB. Itwill limit unnecessary signaling, thereby preventing the consumption ofradio resources. The DeNB informs information as to whether or not theDeNB itself supports the RN using the relay access information. If therelay access information allows an access of the RN, then the RNtransmits RRC Connection Request to the DeNB to request an access.During the process, the RN may inform that the RN itself is a relay whentransmitting RRC Connection Request, Then, the RN may inform a corenetwork that it is a RN through Relay Node Registration using a NASmessage.

According to another embodiment of the present invention, for example,if a bandwidth of 1 Mb/s is required for each voice communication, and acertain DeNB can allocate radio resources corresponding to a bandwidthof 10 Mb/s to a certain RB, then the RN may support the voicecommunications of 10 lines to the maximum for UEs connected to the RNitself. However, if 10 persons now use voice communications among theUEs connected to the RN, then the RN should prevent a new UE from beingaccessed to the RN to perform voice communication. Preferably, the newUE should select a RN or cell which is different from the RN. Thus,according to the present invention, there is provided a method in whichthe RN can effectively perform call admission control (CAC). Preferably,when a new UE attempts an access, it is proposed that the RN informs theDeNB that the new UE has attempted an access. At this time, the RNtransfers the access request information of the UE to the DeNB. Theaccess request information of the UE may include an identifier of theUE, a kind of service that the UE desires to receive, a radio resourceamount of the UE, a priority of the UE, and the like. The DeNB checkswhether or not the UE can be effectively supported based on the accessrequest information of the UE received form the RN, and commands anaccess permission for the UE to the RN if the UE can be supported. TheRN allows an access to the RN to set to a RRC connection only if theaccess permission is received through DeNB; otherwise, the RN rejects aRRC connection. During the process, if the RN rejects a RRC connectionto the UE, then the RN may include information on neighboring cells ormay inform information as to when the UE can attempt an access to the RNagain.

FIG. 13 is another exemplary view illustrating the operation ofcontrolling an access of RN to DeNB and an access of UE to RN accordingto the present invention. As illustrated in FIG. 13, if the UE transmitsRRC Connection Request to attempt an access, then the RN asks DeNBwhether or not an access to the UE is allowed through a process of “RRCConnection Allowed.” If the access is allowed through “RRC ConnectionGranted”, then the RN transmits “RRC Connection Setup” to allow a RRCconnection.

According to another method of the present invention, DeNB transfersinformation of a maximum radio allowance amount or maximum radioresource amount to RN. For example the radio resource amount informationdenotes a maximum number of voice communication users or maximumtransmission bit rate. Thus, if a new UE attempts an access to the RN,and if a radio resource is allocated to the UE but exceeds the maximumnumber of voice communication users or maximum transmission bit rateinstructed from the DeNB, then the RN does not allow an access to theUE. However, if a new UE attempts an access to the RN, and if a radioresource is allocated to the UE but does not exceed the maximum numberof voice communication users or maximum transmission bit rate instructedfrom the DeNB, then the RN allows an access to the UE.

In other words, the DeNB can inform the RN of radio resource amountinformation through a Relay Configuration message as illustrated in FIG.13. In addition, if the UE transmits RRC Connection Request to attemptan access, then the DeNB may determine whether or not it exceeds the setradio resource amount information, thereby determining whether or notradio access to be allowed or not to the UE.

According to the present invention, due to the introduction of a relaynode in an LTE-A system, during a process of transferring data generatedby the UE through a radio network to DeNB which is an end stage of awired network, it may be possible to have an effect of reducing the lossof data blocks and securing the transmission quality of data.

The present invention may provide a method of reporting a status reportin a wireless communication system, the method comprising: receiving, bya first protocol entity, data from a second protocol entity;transmitting, by the first protocol entity, the received data to a thirdprotocol entity; receiving a status report from the third protocolentity, wherein at least one status report indicate any unsuccessfullyreceived data by the third protocol entity: and transmitting the statusreport to the second protocol entity, wherein the first protocol entityis a Relay Node (RN) entity, the second protocol entity is a Donor eNB(DeNB), the third protocol entity is a User Equipment (UE), the allsteps are performed by a Relay Node (RN) entity, the second protocolentity retransmits the data to the first entity upon receiving thestatus report, the all steps are performed in an acknowledged mode radiolink control (AM RLC) layer, and the all steps are performed in a PacketData Convergence Protocol (PDCP) layer.

Hereinafter, a terminal according to the present invention will bedescribed.

A terminal according to the present invention may includes all types ofterminals capable of using services that can transmits and/or receivesdata to and/or from each other in a wireless environment. In otherwords, a terminal according to the present invention may be used in acomprehensive meaning by including a mobile communication terminal (forexample, user equipment (UE), portable phone, cellular phone, DMV phone,DVB-H phone, PDA phone. PTT phone, and the like), a notebook, a laptopcomputer, a digital TV, a GPS navigation, a potable gaming device, anMP3, other home appliances, and the like.

A terminal according to the present invention may include a basichardware architecture (transmission and/or reception unit, processing orcontrol unit, storage unit, and the like) required to perform thefunction and operation for effectively receiving the system informationas illustrated in the present invention.

The method according to the present invention as described above may beimplemented by software, hardware, or a combination of both. Forexample, the method according to the present invention may be stored ina storage medium (for example, internal memory, flash memory, hard disk,and the like, in a mobile terminal or base station), and may beimplemented through codes or instructions in a software program that canbe implemented by a processor (for example, microprocessor, in a mobileterminal or base station), and the like.

Although the present disclosure is described in the context of mobilecommunications, the present disclosure may also be used in any wirelesscommunication systems using mobile devices, such as PDAs and laptopcomputers equipped with wireless communication capabilities (i.e.interface). Moreover, the use of certain terms to describe the presentdisclosure is not intended to limit the scope of the present disclosureto a certain type of wireless communication system. The presentdisclosure is also applicable to other wireless communication systemsusing different air interfaces and/or physical layers, for example,TDMA, CDMA, FDMA, WCDMA, OFDM, EV-DO, Wi-Max, Wi-Bro, etc.

The exemplary embodiments may be implemented as a method, apparatus orarticle of manufacture using standard programming and/or engineeringtechniques to produce software, firmware, hardware, or any combinationthereof. The term “article of manufacture” as used herein refers to codeor logic implemented in hardware logic (e.g., an integrated circuitchip, Field Programmable Gate Array (FPGA), Application SpecificIntegrated Circuit (ASIC), etc.) or a computer readable medium (e.g.,magnetic storage medium (e.g., hard disk drives, floppy disks, tape,etc.), optical storage (CD-ROMs, optical disks, etc.), volatile andnon-volatile memory devices (e.g., EEPROMs, ROMs, PROMs, RAMs, DRAMs,SRAMs, firmware, programmable logic, etc.).

Code in the computer readable medium may be accessed and executed by aprocessor. The code in which exemplary embodiments are implemented mayfurther be accessible through a transmission media or from a file serverover a network. In such cases, the article of manufacture in which thecode is implemented may comprise a transmission media, such as a networktransmission line, wireless transmission media, signals propagatingthrough space, radio waves, infrared signals, etc. Of course, thoseskilled in the art will recognize that many modifications may be made tothis configuration without departing from the scope of the presentdisclosure, and that the article of manufacture may comprise anyinformation bearing medium known in the art.

As the present disclosure may be embodied in several forms withoutdeparting from the spirit or essential characteristics thereof, itshould also be understood that the above-described embodiments are notlimited by any of the details of the foregoing description, unlessotherwise specified, but rather should be construed broadly within itsspirit and scope as defined in the appended claims, and therefore allchanges and modifications that fall within the metes and bounds of theclaims, or equivalents of such metes and bounds are therefore intendedto be embraced by the appended claims.

What is claimed is:
 1. A method of establishing a Radio Resource Control(RRC) connection in a wireless communication system, the methodcomprising: transmitting, from a Relay Node (RN), a RRC connectionrequest message to a Donor eNB (DeNB); receiving, by the RN, a RRCconnection setup message from the DeNB in response to the transmittedRRC connection request message; and transmitting, from the RN, a RRCconnection setup complete message to the DeNB after the reception of theRRC connection setup message, wherein the steps of transmitting the RRCconnection request message, receiving the RRC connection setup message,and the transmitting the RRC connection setup complete message areperformed during a RRC connection establishment, and wherein the RRCconnection setup complete message indicates that the RRC connection isfor the RN only when the RRC connection setup complete message includesinformation indicating that the RRC connection is for the RN.
 2. Themethod of claim 1, wherein, when a User Equipment (UE) receives a PacketData Convergence Protocol (PDCP) Protocol Data Unit (PDU), a cipheringkey is used to decipher the received PDCP PDU.
 3. The method of claim 1,wherein the RRC connection setup complete message is set by a UserEquipment (UE).
 4. The method of claim 1, wherein the RRC connectionsetup complete message is used to confirm a successful completion of theRRC connection establishment.
 5. The method of claim 1, wherein theinformation indicating that the RRC connection is for the RN includes anidentity (ID) of the RN.
 6. A method of establishing a Radio ResourceControl (RRC) connection in a wireless communication system, the methodcomprising: transmitting, from a mobile terminal, a RRC connectionrequest message to a base station; receiving, by the mobile terminal, aRRC connection setup message from the base station in response to thetransmitted RRC connection request message; and transmitting, from themobile terminal, a RRC connection setup complete message to the basestation after the reception of the RRC connection setup message by themobile terminal, wherein the steps of transmitting the RRC connectionrequest message, receiving the RRC connection setup message, and thetransmitting the RRC connection setup complete message are performedduring a RRC connection establishment, and wherein the RRC connectionsetup complete message indicates that the RRC connection is for the RNonly when the RRC connection setup complete message includes informationindicating that the RRC connection is for the RN.
 7. The method of claim6, wherein, when the mobile terminal receives a Packet Data ConvergenceProtocol (PDCP) Protocol Data Unit (PDU), a ciphering key is used todecipher the received PDCP PDU.
 8. The method of claim 6, wherein theRRC connection setup complete message is configured by the mobileterminal.
 9. The method of claim 6, wherein the RRC connection setupcomplete message is used to confirm a successful completion of the RRCconnection establishment.
 10. The method of claim 6, wherein theinformation indicating that the RRC connection is for the RN includes anidentity (ID) of the RN.
 11. An apparatus for establishing a RadioResource Control (RRC) connection in a wireless communication system,the apparatus comprising: a memory; a transceiver; and a processor, theprocessor configured to: transmit, from a mobile terminal, a RRCconnection request message to a base station; receive a RRC connectionsetup message from the base station in response to the transmitted RRCconnection request message; and transmit a RRC connection setup completemessage to the base station after the reception of the RRC connectionsetup message by the mobile terminal, wherein the RRC connection requestmessage is transmitted, the RRC connection setup message is received,and the RRC connection setup complete message is transmitted during aRRC connection establishment, and wherein the RRC connection setupcomplete message indicates that the RRC connection is for the RN onlywhen the RRC connection setup complete message includes informationindicating that the RRC connection is for the RN.
 12. The apparatus ofclaim 11, wherein, when the mobile terminal receives a Packet DataConvergence Protocol (PDCP) Protocol Data Unit (PDU), a ciphering key isused to decipher the received PDCP PDU.
 13. The apparatus of claim 11,wherein the RRC connection setup complete message is configured by themobile terminal.
 14. The apparatus of claim 11, wherein the RRCconnection setup complete message is used to confirm a successfulcompletion of the RRC connection establishment.
 15. The apparatus ofclaim 11, wherein the information indicating that the RRC connection isfor the RN includes an identity (ID) of the RN.